Final Review:Contrast

Question 1

Difference between adjacent gray shades/image receptor exposures

Answer 1

Image Contrast

Question 2

Two photographic factors allow detail to be seen:

Answer 2

-IR exposure
-Contrast

Question 3

Dynamic Range

Answer 3

gray scale, Window Width
Range of brightness displayed on monitor

Question 4

Receptor Exposure

Answer 4

How much is reaching the IR

Question 5

Bit Depth

Answer 5

Shades of gray

Question 6

Determines the dynamic range of image in digital systems (controls contrast)

Answer 6

Look up table

Question 7

Short scale
-few shades of gray between lightest and darkest
-short/narrow dynamic range

Answer 7

High Contrast

Question 8

Long scale
-more shades of gray between lightest and darkest
-large/ wide dynamic range

Answer 8

Low Contrast

Question 9

Why is high contrast not necessarily a good thing in medial imaging

Answer 9

More shades of gray can reveal more information

Question 10

Manipulating contrast

Answer 10

Compression or expansion of range of visible densities
-adjustment to kvp
-Window width left and right

Question 11

Subject contrast is dependent on:

Answer 11

-kvp
-amount of irradiated material
-Type of irradiated material

Question 12

What causes wider range of photon energy?

Answer 12

-greater penetrability
-greater range of exposures
-greater amount of scatter
-longer scale of contrast (film)

Question 13

Higher kvp produces how much range of exposure

Answer 13

narrower range of exposures picked up by IR (yields a narrower histogram)

Question 14

Excessive kvp’s reduce differential absorption and therefore limits the range of exposure values picked up by the IR. What can this lead to

Answer 14

Can lead to histogram errors

Question 15

If the kvp does not match the subject contrast, what is being impacted?

Answer 15

Differential absorption

Question 16

Increase in thickness and field size does what to the scatter and scale of contrast?

Answer 16

-increases scatter
-longer scale of contrast (film)

Question 17

The amount of irradiated material is dependent on:

Answer 17

Thickness or part and field size

Question 18

Type of irradiated material is influenced by:

Answer 18

Atomic number and tissue density

Question 19

What does high atomic number and tissue density do to attenuation and photoelectric interactions

Answer 19

-greater attenuation
-more photoelectric interactions

Question 20

Large differences in atomic number and tissue density of adjacent tissues

Answer 20

High Contrast

Question 21

What is the primary controlling factor for the the patient

Answer 21

kvp

Question 22

Why can’t the subject contrast be manipulated

Answer 22

Because it is the patient (tissue)

Question 23

For a nongrid, what number should you not exceed?

Answer 23

80 kvp

Question 24

Cannot be assessed by visualization

Answer 24

kvp

Question 25

what scatter ration requires use of grids

Answer 25

greater than 50%

Question 26

does focal spot effect contrast?

Answer 26

No affect of contrast

Question 27

how does more matter affect contrast

Answer 27

decreases contrast

Question 28

how does collimation affect contrast

Answer 28

Increased collimation increases contrast and decreases scatter

Question 29

does the anode heel affect have any affect on contrast

Answer 29

no effect on contrast but effects receptor exposure

Question 30

does SID affect contrast

Answer 30

SID only affects receptor exposure, not contrast

Question 31

Air Gap Technique

Answer 31

6 to 8 inch gap to decrease scatter on IR. Increases contrast because scatter is not reaching IR.

Question 32

Increased filtration decreases quantity but increases quality

Answer 32

Filtering out low energy photons

Question 33

Increased filtration, decreased ESE

Answer 33

More to IR, less absorption. More transmission, filtering out low energy photons

Question 34

Increased Filtration does what to beam energy and contrast?

Answer 34

Increased average beam energy and decreased contrast (film)

Question 35

How is grid ratio and contrast related?

Answer 35

Directly. Increased grid ration increases contrast (more black and white because more clean up removing scatter)

Question 36

Differences in density between two areas on an image

Answer 36

contrast

Question 37

Long scale contrast

Answer 37

many shades of gray visible

Question 38

short scale contrast

Answer 38

mostly blanks and whites present

Question 39

Large differences in density

Answer 39

high contrast

Question 40

small density differences

Answer 40

low contrast

Question 41

Range of exposures that will produce radiograph in the diagnostic range of densities

Answer 41

Exposure Latitude

Question 42

Latitude inverse relationship to contrast:

Answer 42

Wide latitude = low contrast Narrow latitude = high contrast

Question 43

Latitude relationships to gray scale:

Answer 43

Wide latitude= long gray scale contrast Narrow latitude= short gray scale contrast

Question 44

Example of long scale contrast:

Answer 44

Abdominal xrays or chest xrays

Question 45

Example of short scale contrast:

Answer 45

Hand xrays (bony anatomy)

Question 46

Look up table

Answer 46

Picture perfect image, manipulates values of gray levels, controlling contrast

Question 47

is brightness in film or digital

Answer 47

digital (monitor)

Question 48

Is density film or digital

Answer 48

Film

Question 49

What are some of your subject contrast?

Answer 49

kvp amount of irradiated material type or irradiated materal

Question 50

Differential absoprtion

Answer 50

Will it either transmit or absorb

Question 51

Window width Window leveling Annotation Any manipulation to an image

Answer 51

Post processing

Question 52

Bit depth Look up table Histogram

Answer 52

Pre processing